Studies on sign language grammaticalization have demonstrated that most of the attested diachronic changes from lexical to functional elements parallel those previously described for spoken languages. To date, most of these studies are either descriptive in nature or embedded within functional-cognitive theories. In contrast, we take a generative perspective on sign language grammaticalization, adopting ideas by Roberts &#38; Roussou (2003), who suggest that grammaticalization can be characterized as &#8220;reanalysis &#8216;upwards&#8217; along the functional structure&#8221;. Following an overview of some of the attested modality-independent pathways, we zoom in on the grammaticalization of two types of agreement auxiliaries, the lexical sources of which are the verb GIVE and the noun PERSON. We argue that the grammaticalization of GIVE-AUX (in Greek Sign Language and Catalan Sign Language) follows directly from Roberts &#38; Roussou&#8217;s model because a lexical verb is reanalyzed as an element which is merged in a structurally higher functional position (little v). The same is true for PERSON, but this change has an additional modality-specific flavor. In spoken languages, agreement affixes typically enter the functional domain of V via cliticization. In contrast, in German Sign Language and Catalan Sign Language, PERSON, after having been reanalyzed as a determiner-like element, &#8216;jumps&#8217; directly from D into AgrO &#8212; most probably because it has the relevant spatial properties necessary to express agreement. Thus, grammaticalization in sign languages, while being structurally similar, allows for types of reanalysis that are not attested in spoken languages.